Pneumatic tires

ABSTRACT

A tire of reduced weight and greater strength is obtained by restraining the radial carcass on the inside by means of a shoulder ply arranged on the inside of the carcass at each end of the crown reinforcement so as to impart a nearly rectangular meridian profile to the carcass.

United States Patent Verdier Feb. 5, 1974 PNEUMATIC TIRES 5,703,20311/1972 Simpson 152/354 [75] Inventor: Henri Verdier, Beauregard-LEveque, France FOREIGN PATENTS OR APPLICATIONS Assigneez c pagnieGenerale D s Switzerland Establissements Michelin, raison socialeMichelin 8L Cie,

Primary Examiner-Gerald M. Forlenza Clement Ferrand France AssistantExaminer-Robert Saifer [22] Filed: June 9, 1972 Attorney, Agent, orFirm-Granville M. Brumbaugh et 21 Appl. No.: 261,379

[30] Foreign Application Priority Data June 15, 1971 France 7121773ABSTRACT [52] US. Cl. 152/356, 152/361 R A tire of reduced weight andgreater strength is ob- [51] Int. Cl. B60c 9/04, B60c 9/18 tained byrestraining the radial carcass on the inside [58] Field of Search...152/350, 354, 355, 356, 357, by means of a shoulder ply arranged on theinside of 152/359, 361 the carcass at each end of the crownreinforcement so as to impart a nearly rectangular meridian profile to[56] References Cited the carcass.

UNITED STATES PATENTS 6/1968 Massoubre 152/361 8 Claims, 3 DrawingFigures PNEUMATIC TIRES The object of the present invention isimprovements in radial-carcass pneumatic tires, said improvementsrelating more particularly to the structure of the junction of the crownof the tire with the sidewalls.

As is known, a radial carcass tire has a double reinforcement, namely acrown reinforcement which reinforces the tread and a carcassreinforcement which reinforces the sidewalls and connects them to thecrown. The carcass reinforcement, which is flexible and deformable, isformed of wires or cords arranged in radial planes of the tire. Thecrown reinforcement, which is rigid and relatively nondeformable, isformed of a stack of cord plies, preferably of metal, arranged in twoand preferably three different directions.

The connecting of reinforcements which are so dissimilar raises adifficult problem. The difficulty resides in the great difference inshape and deformability of their meridian profiles.

Under the action of the inflation pressure, the crown reinforcement hasa tendency to assume a slightly curved, practically flat meridianprofile. Moreover, this profile changes little when the meridian sectionwhich contains it comes into the area of contact of the tire with theroad. Moreover, the angular arrangement of the cords of the crownreinforcement is selected in order to obtain a slightly curved meridianprofile, so that the tread and the crown reinforcement travel on theground with minimum distortion.

The carcass reinforcement is entirely different. Under the action of theinflation pressure, it has a tendency to assume a relatively curvedmeridian profile. Moreover, the meridian profile changes greatly whenthe section which contains it turns around the axis of rotation of thetire; it is, as a matter of fact, the carcass which undergoes thegreatest deformation in that region of the tire which contacts theground. Furthermore, the meridian profile of the carcass is subject tothe greatest variations of curvature in the zone near the tread.

The solution adopted for connecting the crown reinforcement and thecarcass reinforcement consists in providing between them a layer ofrubber which is of small or zero thickness in the vicinity of thecentral plane of the tire progressively increasing in thickness towardsthe edges of the crown reinforcement. These wedges of rubber have therole of taking up the difference between the curvatures of the tworeinforcements and of absorbing the changes in curvature of the carcassduring travel. They form an elastic bond which permits the cooperationof two types of reinforcements which are fundamentally different andhave different functions.

lt will readily be understood that this arrangement is not without itsdrawbacks.

The first and principal drawback is that the tire has an excessthickness in the region of the shoulders and of the edges of the crownreinforcement and this in a zone which is stressed a good deal. As amatter of fact, to the extent that the difference in curvature which thecrown reinforcement and carcass reinforcement naturally present iscompletely taken up, one is compelled to use thicker wedges of rubber,which favors an accumulation of heat. If the difference in curvature isnot fully taken up, the rubber wedges are thinner but the amount of thestresses is greater.

This drawback is obviously greater in the case of tires employing a widetread which fully covers the region of the shoulder, that is to say, theregion of the junction of the crown with the sidewalls.

A second drawback is that the carcass reinforcement produces harmfulstresses whenever its molded profile does not correspond strictly to itsequilibrium profile. In particular, the outer covering of the tire maybe stretched, which favors cracks and tears in the tread grooves in theregion of the shoulder. Similarly, the inner covering of the tire may attimes be sheared by the cords of the carcass.

The present invention is directed at alleviating these drawbacks, doingthis by correcting the insufficiently curved meridian profile of thecarcass so as to bring the meridian profiles of the carcassreinforcement and of the crown reinforcement close to each other andfacilitate the connecting of them.

The pneumatic tire in accordance with the invention comprising acontinuous carcass formed of radial wires or cords and a crown pliedreinforcement which reinforces the tread, has a slightly curved meridianprofile and restrains the carcass on the ouside, is characterized by thefact that the carcass is restrained on the inside by at least oneshoulder ply of elastic wires or cords forming an angle of at most 30with respect to the ra dial wires or cords of the carcass, said shoulderply being separately arranged on the inside of the carcass at each endof the crown plied reinforcement.

By elastic wires or cords there is understood a wire or cord having anelongation at rupture of more than 6 percent.

ln accordance with various preferred embodiments:

a. the carcass is restrained on the inside by two shoulder plies ofelastic wires or cords intersecting from one ply to the other,

b. the elastic wires or cords of the shoulder ply are inclined by anangle of 10 to 20 to the radial wires or cords of the carcass,

c. the elastic wires or cords of the shoulder ply are arrangedsymmetrically with respect to the carcass wires or cords,

d. the shoulder plies which restrain the carcass on the inside extendsubstantially over the same width on either side of each edge of thecrown piled reinforcement, the difference in width not exceeding 20percent,

e. the total width of each shoulder ply which restrains the carcass onthe inside is substantially equal to half the width of the widest crownply, the difference not exceeding 20 percent,

f. the elastic wires or cords of the shoulder ply are made of syntheticfibers, for instance, polyamide fibers.

It is essential in accordance with the invention that the carcass bereinforced and restrained on the inner side. It is a question of raisingthe profile of the carcass in the direction of the crown reinforcementby preventing the displacement of said profile towards the inside of thetire. The carcass is thus sandwiched between the crown reinforcement andthe additional reinforcement provided in accordance with the invention.

It is essential that the additional reinforcement extend at each edge ofthe crown reinforcement. It is a question, as a matter of fact, of notonly raising the meridian profile of the carcass in the direction of thetread, but furthermore of widening it in the direction towards theoutside of the sidewalls.

It is finally essential to use elastic wires or cords which are slightlyinclined with respect to the radial wires or cords of the carcass inorder not to reduce the flexibility of the sidewalls in excessive andundesirable fashion. Moreover, elastic wires or cords which areexcessively inclined with respect to the radial wires or cords of thecarcass would make the shaping of the carcass difficult.

The arrangements described have the effect of raising the meridianprofile of the crown of the carcass. This profile is more rectangularthan in the absence of internal reinforcement, without the profile ofthe bottom zone of the carcass being substantially changed. Moreover,the region of the sidewalls of maximum width is brought close to thecrown and the tension of the carcass wires is accordingly decreased.

The decrease in the disparity of the meridian profiles of the carcassand the crown reinforcement has the consequence of improving thecoherence between the two reinforcements and reducing the thickness ofthe wedges of rubber forming the elastic connection between them. Notonly is an appreciable reduction in weight obtained, but one also gainsin strength. Subsidiarily, the auxiliary reinforcement which restrainsthe carcass on the inside reduces the stretching of the outer coveringof the shoulder and prevents the shearing of the inner covering by thecords of the carcass.

The invention will be clearly understood from a representative exampleillustrated in the accompanying drawings in which:

FIG. 1 is a radial or transverse cross section through a tire inaccordance with the invention,

FIG. 2 shows, seen in enlarged plan view, the portion of the tirereinforcement enclosed by a circle in FIG. 1, and

FIG. 3 shows in solid line the meridian profile of the carcass of thetire of FIG. 1 and in dashed line the meridian profile of a carcass of atire which is not restrained on the inside.

FIG. 1 shows in radial or transverse cross section a tire I inaccordance with the invention of size 33.533. This therefore is a tireof very large size for construction equipment, weighing about 900 kg. Ofcourse, the invention is not limited either to such size or to such typeof tire.

This tire has a very wide tread 2 in accordance with U.S Pat. No.3,457,981, having lateral protuberances 3, and sidewalls 4 terminatingin beads 5.

Its reinforcement is composed first of all ofa continuous carcassreinforcement 6 composed of radial metal cords anchored around two beadwires 7 and extending up again in the sidewall substantially to themidheight of the sidewall 4. Secondly, it comprises a crown pliedreinforcement containing in succession:

two narrow plies 10 of metal cords inclined by an angle of 65 to theleft with respect to the circumferential direction.

a narrower ply 12 of metal cords inclined by an angle of 24 towards theright,

two plies l3 and 14 of elastic metal cables inclined by an angle of 24to the left and to the right respectively.

In accordance with the invention, the carcass 6 is reinforced by twoshoulder plies l6 and 17 of polyamide cords spanning each of the edges11A and 11B of the ply 11 and extending over substantially equaldistances. The shoulder plies l6 and 17 have a width which correspondsapproximately to half the width of the widest crown ply 11. Theseshoulder plies l6 and 17 are placed in accordance with the inventionbelow or inside the carcass 6. The polyamide cords of which they arecomposed are formed of two strands of a denier of 1880 decitex. Theystretch 8 percent for a load corresponding to one-quarter of the ruptureload. They are arranged in a density of I20 cords per decimeter of widthof the ply.

The cords of the shoulder plies 16 and 17, as can be noted from FIG. 2,are inclined by an angle of about 15 to the radial cords of the carcass6, that is to say, by an angle of about to the circumferentialdirection.

FIG. 3 shows superimposed the meridian profile I of the carcass of thetire of FIG. 1 and meridian profile II of the carcass of a tire which isidentical except that it does not have the shoulder plies 16 and 17.

As can be seen, the meridian profile I of a carcass in accordance withthe invention which is restrained both on the outside and on the insideis much more rectangular, that is to say closer both to the cylinder Ccircumscribed around the carcass along the median line S of the crownand the planes P perpendicular to the axis of the tire and tangent tothe sidewalls. Moreover, the meridian profile I is tangent to the planeP along a parallel circle of tangency E, of larger diameter than theparallel circle of tangency E of the conventional meridian profile II.

FIG. 3 shows the advantage of the invention. As a matter of fact, bybringing the meridian profile of the carcass towards the outer profileof the tire, one saves an appreciable amount of rubber (hatched zone)corresponding to the difference in the surfaces bounded by the profilesI and II. In the case of a tire of the size 33.5-33, the saving is 72 kgof rubber, namely, about 8 percent of the weight. Moreover, thethickness of the tire is decreased in a region where it is generallyexcessive and where it produces undesirable heating upon travel. Thislast-mentioned advantage is particularly substantial in the case of atire having a wide tread which is continued into the sidewalls, as inthe case of FIG. 1.

As can be seen, the shoulder plies l6 and 17 of elastic ,cordssubstantially and unexpectedly modify the geometry of the tire and in amanner which is both simple and effective, correct the tendency of aradial carcass to move away from a substantially cylindrical crownreinforcement. If one takes the precaution of internally restraining thecarcass, without making it rigid, by using elastic cords of only slightinclination to the cords of the carcass, the flexibility of the tire ischanged very little.

It goes without saying that without going beyond the scope of theinvention, various changes could be made in the example described. Theessential thing is to restrain the carcass on the inside, at each edgeof the crown reinforcement, without thereby removing its flexibility.

What is claimed is:

l. A tire comprising a continuous carcass formed of radial wires orcords and a crown plied reinforcement which reinforces the tread, has aslightly curved meridian profile and restrains the carcass on theoutside, characterized by the fact that the carcass is restrained on theinside by at least one shoulder ply of elastic wires or cords forming anangle of at most 30 with respect to the radial wires or cords of thecarcass, said shoulder ply being separately arranged on the inside ofthe carcass at each end of the crown plied reinforcement, whereby themeridian profile of the carcass is raised in the direction of the crownplied reinforcement.

2. The tire as defined by claim 1 wherein the carcass is restrained onthe inside by two shoulder plies of elastic wires or cords havingopposite angularity.

3. The tire as defined by claim 1 wherein the elastic wires or cords ofsaid shoulder ply which restrains the carcass on the inside form anangle of between and with respect to the radial wires or cords of thecarcass.

4. The tire as defined by claim 1 wherein the said shoulder ply ofelastic wires or cords extends substantially over the same width oneither side of each edge of the crown plied reinforcement.

5. The tire as defined by claim 1 wherein the said shoulder ply ofelastic wires or cords has a width substantially equal to one-half ofthe width of the widest crown ply.

6. The tire as defined by claim 1 wherein the elastic wires or cords ofthe shoulder ply consist of synthetic fibers.

7. The tire as defined by claim 1 wherein the carcass has asubstantially rectangular meridian profile comprising a central portioncovered by the crown reinforcement and spaced only slightly from it andtwo lateral portions substantially parallel to the median plane and alsoonly slightly curved, the central portion and the lateral portions beingconnected by strongly curved connections of small developed length.

8. The tire as defined by claim 1 wherein the tread has a widthsubstantially equal to that of the carcass and a distance from thecarcass substantially constant at all points of its outer surface.

"H050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3789, 900 Dat d February 5 1974 Inventor) Henri Verdier It iscertifiedthat error appears in the above-identified patent and that saidLetters Patent are hereby corrected as shown below:

On face of patent, first column, after "Inventorz",

"Henri Verdier, Beauregard-L Eveque, France" should read Henri Verdier,Beauregard- L'Eveque, France Column 2, line 46, "piled" should readplied Column 3, between lines 57 and 58, the following paragraph shouldbe inserted: a wide ply ll of metal cords inclined by an angle of 24towards the left at the middle of the ply,

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

C. MARSHALL DANN Commissioner of Patents MCCOY M. GIBSON JR. AttestingOfficer

1. A tire comprising a continuous carcass formed of radial wires orcords and a crown plied reinforcement which reinforces the tread, has aslightly curved meridian profile and restrains the carcass on theoutside, characterized by the fact that the carcass is restrained on theinside by at least one shoulder ply of elastic wires or cords forming anangle of at most 30* with respect to the radial wires or cords of thecarcass, said shoulder ply being separately arranged on the inside ofthe carcass at each end of the crown plied reinforcement, whereby themeridian profile of the carcass is raised in the direction of the crownplied reinforcement.
 2. The tire as defined by claim 1 wherein thecarcass is restrained on the inside by two shoulder plies of elasticwires or cords having opposite angularity.
 3. The tire as defined byclaim 1 wherein the elastic wires or cords of said shoulder ply whichrestrains the carcass on the inside form an angle of between 10* and 20*with respect to the radial wires or cords of the carcass.
 4. The tire asdefined by claim 1 wherein the said shoulder ply of elastic wires orcords extends substantially over the same width on either side of eachedge of the crown plied reinforcement.
 5. The tire as defined by claim 1wherein the said shoulder ply of elastic wires or cords has a widthsubstantially equal to one-half of the width of the widest crown ply. 6.The tire as defined by claim 1 wherein the elastic wires or cords of theshoulder ply consist of synthetic fibers.
 7. The tire as defined byclaim 1 wherein the carcass has a substantially rectangular meridianprofile comprising a central portion covered by the crown reinforcementand spaced only slightly from it and two lateral portions substantiallyparallel to the median plane and also only slightly curved, the centralportion and the lateraL portions being connected by strongly curvedconnections of small developed length.
 8. The tire as defined by claim 1wherein the tread has a width substantially equal to that of the carcassand a distance from the carcass substantially constant at all points ofits outer surface.